The present invention relates to feed-through devices subject to harsh environments, and more particularly, the present invention relates to a feed-through device, such as an electrical or optical feed-through device, that is hermetically sealed.
An electrical or optical feed-through device enables electrical or optical continuity from inside a sealed chamber or vessel through a wall of the chamber or vessel to a location external of the chamber or vessel. The feed-through device must be able to withstand the harsh environment within the chamber or vessel without permitting the creation of leakage paths out of, or into, the sealed chamber or vessel.
Examples of feed-through devices include: terminal feed-through devices for lithium batteries and other electrochemical devices having corrosive electrolytes; instrumentation electrical and RF feed-through devices for chemical reactor vessels; thermocouple feed-through devices for heat treating atmospheres and vacuum furnaces and environmental test chambers; and electrical power feed-through devices for controlled atmosphere furnaces and ovens. Also, see U.S. Pat. No. 4,982,055 issued to Pollack et al. which discloses a sealed electrical feed-through device, and U.S. Pat. No. 6,351,593 B1 issued to Pollack et al. which discloses a hermetically-sealed optical feed-through device.
Sealed electrical terminal feed-through devices typically utilize glass-to-metal, ceramic-to-metal, or molded plastic-to-metal seal technologies. The materials from which the terminal and insulator components of the devices are made are required to have substantially matching thermal coefficients of expansion over the end use operating temperature performance range of the devices to ensure that hermetic seals are maintained. Accordingly, this limits material choices and performance capabilities. In addition, the selection of the material used for the seal components is further limited due to the required fabrication process temperatures used during manufacture of the devices; because, the fabrication process temperatures are typically greater then the performance operating range of the devices.
Accordingly, there is a need for a feed-through device providing enhanced performance capabilities and a method for making a feed-through device that enables such extended capabilities to be achieved. The method of manufacturing the devices should permit the selection of materials for the terminal and insulator components from a wider variety of materials then currently permitted. The selected materials should provide the device with enhanced corrosion resistance capabilities and should reduce galvanic-induced corrosion and provide a longer lasting seal.